Electron emitting cathodes, discovered in the 19th century, were the subject of Einstein's first Nobel Prize, and the basis of the vacuum tubes that created modern electronics. Although transistors have overtaken them in general electronics, many modern devices still use electron emitting cathodes. However, these cathodes would be more practical if they could endure long periods of operation in contaminating environments—electron lithography for example. Contamination remains an open problem because such environments can reduce the lifetime of cathode materials within hours, while the practical lifetime needs to be days or years. A need exists for an electron transparent pellicle, able to efficiently operate at lower voltages, that protects an electron emitter from contamination.
It should be noted that the figures are not drawn to scale and that elements of similar structures or functions are generally represented by like reference numerals for illustrative purposes throughout the figures. It also should be noted that the figures are only intended to facilitate the description of the preferred embodiments. The figures do not illustrate every aspect of the described embodiments and do not limit the scope of the present disclosure.